According to George S. Chuaj and William Brandimore on the Numismaster.com website, "The First Issue of U.S. Government stamp money is the only one of the five issues to be identified by name as Postage Currency. The initial printing of the First Issue was released through Army paymasters on Aug. 1, 1862, and was provided for general circulation a few weeks later."
They go on to say, "Although it is a moot point, Postage Currency probably constitutes an illegal issue of fractional notes. Rather than being strictly 'postage and other stamps of the United States,' and despite being 'receivable for postage stamps at any U.S. post office,' Postage Currency took the form of reproductions of postage stamps printed on paper which carried the promise of the United States to exchange the currency for United States Notes, which gave Postage Currency the attributes of a promissory note, a development beyond the intent of the enabling Act of July 17, 1862."
Chuaj and Brandimore point out, "An interesting feature of the First Issue is the existence of notes with both perforated and straight edges. Apparently, the idea of perforated Postage Currency was a carry-over from the postage stamp printing process and was discarded when the demand for Postage Currency exceeded the capacity of the perforating machines."
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